Method and apparatus for blow molding

ABSTRACT

A method and apparatus for blow molding an article wherein a parison is positioned between substantially opposed mold closures. The opposed mold closures and at least one other mold closure are advanced, wherein the at least one other mold closure is advanced into abutment with at least one of another of the substantially opposed mold closures, and another of the at least one other mold closure. Thereafter, a gas may be injected within the interior of the parison to form a molded article, the mold closures retracted along their respective axes, and the molded article removed.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.10/646,677 filed Aug. 22, 2003 now abandoned.

FIELD OF THE INVENTION

This invention relates generally to molding processes and apparatusesand more particularly to plastic blow molding processes and apparatuses.

BACKGROUND OF THE INVENTION

Blow molding is a well known method for producing a variety of plasticproducts, particularly hollow vessels including fuel tanks, containers,and the like. As depicted in FIG. 1, a blow molding process andapparatus M typically involves spreading portions of a heated pre-formedplastic article A between two spreader pins P. As shown, blow moldingprocesses almost universally involve molding the hot pre-formed articleA between two mold halves Hl and Hr, which open away from one anotherand close together along a single axis X.

One variation on this concept is disclosed in U.S. Pat. No. 5,198,174 toNakagawa et al. Nakagawa et al is directed toward the problemsassociated with forming a radially extended flange portion at one end ofa hollow plastic product, such as a flanged pipe. Nakagawa et al.asserts that it is nearly impossible to simultaneously and integrallyblow mold a tubular portion with a hollow head or a radially extendingflange portion at one end of the tubular portion due to unacceptablethinning of the material at the corners of the flange portion.Therefore, Nakagawa et al instead teach a method of blow molding thetubular portion and then injection molding a solid radially extendingflange portion on the tubular portion. Nakagawa et al disclose a blowmold having a pair of mold closures or mold halves that close toward oneanother along an axis. Each of the mold halves includes a recess and amating surface. When the mold halves come toward one another, theirrespective mating surfaces engage one another to close the mold. Inother words, the closed mold is established by the closure of the moldhalves together such that the mating surfaces engage. A first moldcavity is defined not only by the recesses of the mold halves, but alsoby movable mold segments that are mounted within the mold halves andthat are moved to an advanced position within the mold halves. The firstmold cavity is provided to blow mold the tubular portion of the hollowarticle. A second mold cavity is defined by the movable mold segmentswhen they are moved to a retracted position within the mold halves. Thesecond mold cavity is provided to injection mold the solid flangeportion of the hollow article.

Another variation is disclosed in U.S. Patent Application Publication2002/0171161 to Belcher. Belcher identifies several problems withcombining blow molding and injection molding operations to form a singlehollow article, such as a bottle with a handle. Belcher teaches a methodof blow molding a bottle and thereafter pinching side walls of the blownbottle so as to bond adjacent interior wall surfaces together to formthe handle. Belcher discloses a blow mold having two mold closures; afront half section and a rear half section that define the front andrear of the bottle and traverse toward one another along an axis. Bothhalf sections have mating surfaces that engage one another to close themold and define a mold cavity, wherein the bottle is expanded or blown.A movable mold segment is mounted within each of the half sections tomove along an axis that is parallel to the closure axis. The movablemold segments are linearly opposed and move toward one another from aretracted position to an advanced position to pinch opposed portions ofthe blown bottle together to form an integral handle.

Thus, the Nakagawa et al and Belcher references both teach theconventional method of closing a mold by bringing two mold closures ormold halves together. Unfortunately, however, the use of two mold halvesto close a blow mold has some drawbacks. Referring again to FIG. 1, moldhalves Hl and Hr engage one another along mating engagement surfaces Sland Sr in a closed position as shown. During a blowing step, relativelylarge portions of the pre-formed article A tend to get pinched betweenthe mating engagement surfaces Sl and Sr of the mold halves Hl and Hr,which is an undesirable condition. As shown in FIG. 2, this pinchingphenomenon creates a heavy parting line L in a finished blow moldedarticle B. Pinching of pre-formed material and resulting heavy partinglines are especially problematic when blow molding a multi-layerarticle, such as that shown, which includes a relatively thin andfragile inner membrane I. Due to the pinching of the pre-formed articlebetween the mold halves, such membranes can become ruptured in variousplaces along the parting line, as shown by rupture R. Ruptured membranesare undesirable, especially when the purpose of such membranes is toprevent vapor permeation through the wall of the finished blow moldedarticle. Specifically, hydrocarbon vapors can escape to atmospherethrough the walls of a fuel tank through such ruptured membranes.

Another problem associated with conventional blow molding processes andapparatuses involves unnecessarily high stretch ratios of pre-formedarticles. In other words, conventional blow molding typically involvesusing parisons or pre-formed articles, wherein portions thereof must beblown or expanded to two to three times their original size in order toachieve the final dimensions of the finished blow molded article.Accordingly, some portions of the pre-formed article will experience ahigh stretch ratio, thereby resulting in significant thinning of thewall thickness of those portions, as discussed in the Nakagawa et al.reference. In contrast, other portions of the pre-formed article willexperience a low-stretch ratio, thereby resulting in relatively littlethinning. This significant difference in stretch ratios over theentirety of the pre-formed article tends to result in a finishedblow-molded component with a wall thickness distribution that issubstantially non-uniform.

SUMMARY OF THE INVENTION

A method of blow molding an article from a parison within a blow mold,including the steps of providing substantially opposed mold closures andat least one other mold closure; positioning a parison between thesubstantially opposed mold closures; and advancing the substantiallyopposed mold closures and the at least one other mold closure, includingadvancing the at least one other mold closure into abutment with atleast one of: another of the substantially opposed mold closures, andanother of the at least one other mold closure.

A method of blow molding an article which generally includes the stepsof positioning a parison between three or more mold closures, advancingthe mold closures along two or more axes to close the mold closuresaround the parison, and blow molding the parison to produce the article.More specifically, the method of making the article may include thesteps of: positioning a parison between multiple mold closures;advancing one or more of the multiple mold closures along a first axisand advancing one or more other of the multiple mold closures alonganother axis, which is generally transverse to the first axis; injectinga gas within the interior of the parison; retracting the mold closuresalong their respective axes; and removing a molded article formed fromthe parison. Articles are also produced by the processes describedabove.

An apparatus for blow molding an article from a parison is provided. Theapparatus includes substantially opposed mold closures that are moveablebetween open and closed positions. At least one other mold closure istranslatably mounted to at least one of the substantially opposed moldclosures. The at least one other mold closure is moveable between openand closed positions, and into abutment with at least one of another ofthe substantially opposed mold closures, and another of the at least oneother mold closure.

Preferably, the apparatus includes first and second opposed moldclosures that are moveable between open and closed positions along anaxis. The apparatus further includes one or more other mold closuresthat are translatably mounted to the first and second opposed moldclosures and are moveable between open and closed positions alonganother axis.

Objects, features, and advantages of this invention include providing anapparatus and method for producing an article that improves the surfacequality and internal integrity of a blow molded article, reduces thehydrocarbon permeability of a blow molded fuel tank, reduces the stretchratio of a blow molding operation, enables blow molding of flangeportions, enables use of a relatively larger parison than beforepossible, eliminates the need to use pinch plates and pre-blowing,better facilitates the blow molding of a fuel tank around a carrier toproduce a “Ship-In-a-Bottle” article that is of relatively simpledesign, economical manufacture and assembly, and has a long servicelife.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of this invention willbe apparent from the following detailed description of the preferredembodiments and best mode, appended claims, and accompanying drawings inwhich:

FIG. 1 is a cross-sectional view of a blow molding apparatus inaccordance with the prior art;

FIG. 2 is a partial cross-sectional view of a prior art blow moldedcomponent manufactured using the prior art apparatus of FIG. 1;

FIG. 3A is a partial cross-sectional view of a blow molding apparatus inan open or retracted position, according to an embodiment of the presentinvention;

FIG. 3B is a partial cross-sectional view of the blow molding apparatusof FIG. 3A along lines 3B-3B, illustrating spreader pins engaging alower portion of a parison;

FIG. 3C is a partial cross-sectional view of the blow molding apparatusof FIG. 3A, illustrating the spreader pins fully extended and a blow pinmechanism and a carrier extending up into the parison;

FIG. 4 is a cross-sectional view of the blow molding apparatus of FIG.3A in a closed or advanced position with the parison fully spread by thespreader pins;

FIG. 5A is a partial cross-sectional view of the blow molding apparatusof FIG. 3A, illustrating gas being injected through the blow pin tofully expand the parison;

FIG. 5B is a cross-sectional view of the blow molding apparatus of FIG.3A, illustrating the parison being fully blown into final position;

FIG. 6 is a partial cross-sectional view of a blow molded componentproduced by the apparatus of the present invention and/or in accordancewith the method of the present invention;

FIG. 7 is a top view of a parison positioned within a blow moldingapparatus according to another exemplary embodiment of the presentinvention;

FIG. 8 is a front perspective view of the blow molding apparatus of FIG.7;

FIG. 9 is a top view of the parison positioned within the blow moldingapparatus of FIG. 7;

FIG. 10 is a rear perspective view of the blow molding apparatus of FIG.9;

FIG. 11 is a cross-sectional view of the blow molding apparatus of FIG.7 illustrating a fully closed position; and

FIG. 12 is a perspective view of a fuel tank as an exemplary article ofmanufacture that may be produced by one or more exemplary methodsaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring in detail to the drawings, FIG. 3A illustrates a blow moldingapparatus 10 of the invention, which is constructed for use with a blowmolding machine 12. The blow molding apparatus 10 is depicted in crosssection, looking downward along a Z axis with an X axis extending leftto right and a Y axis extending rear to front. As defined herein, X, Y,and Z are orthogonal axes and each axis represents a relative direction,rather than a specific line along that direction. Moreover, the termsleft, right, front, and rear are used as an expedient for more clearlyexplaining the present invention, and are not to be interpreted aslimiting the present invention to the orientations described herein. Theblow molding apparatus 10 includes left and right base frames 14 and 16that are attached to left and right movable platens or mold closers 18and 20 of the blow molding machine 12. The base frames 14 and 16 may beconstructed in an open space frame configuration as is well known in theart, such as from a weldment or a casting, such that hydraulic lines,coolant lines, and the like can be routed therethrough. Likewise, themold closers 18 and 20 are well-known in the art and are typicallycomponent parts of the blow molding machine 12 that are activatedhydraulically.

Unlike prior art blow molding apparatuses that only include two opposedmovable mold halves, the blow molding apparatus 10 of the presentinvention includes a plurality of movable mold closures or segments,which are shown in FIG. 3A in a retracted or open position. Theplurality of movable mold segments includes a left mold segment 22mounted on the left base frame 14 and a right mold segment 24 mounted onthe right base frame 16. Accordingly, the mold closers 18 and 20 arecapable of traversing the left and right mold segments 22 and 24 betweenopen and closed positions along the X axis. Rear and front left moldsegments 26 and 30 are slidably mounted to the left segment 22, and rearand front right mold segments 28 and 32 are slidably mounted to theright segment 24. Thus, the rear and front mold segments 26, 28 and 30,32 are slidable between open and closed positions along the Y axis. Asshown, the rear and front mold segments 26, 28 and 30, 32 moveperpendicularly transverse to the X axis motion of the left and rightmold segments 22, 24. However, the mold segments 22, 24, 26, 28, 30, 32may move in any generally oblique or transverse directions with respectto one another. Each of the mold segments 22, 24, 26, 28, 30, 32 ispreferably jacketed with cooling passages therethrough as is well knownin the art.

The rear and front mold segments 26, 28 and 30, 32 need not be mountedto their respective left and right mold segments 22 and 24, but insteadcould be separately mounted to the blow molding machine 12, such as byrear and front mold closers (not shown), similar to the left and rightmold closers 18 and 20. While this specific mounting configuration ofthe mold segments and closures of the present invention is particularlycost effective, it is contemplated that other, more complex moldsegments and closure arrangements could be provided and still fall wellwithin the scope of the present invention. For example, three or moremold segments could be arranged radially with respect to a commoncenter, wherein the mold segments advance radially inwardly toward thecommon center.

In any case, each of the left and right mold segments 22 and 24 includesmold surfaces 22 a and 24 a, which partially define a mold cavity 34.The mold cavity 34 is further defined by mold surfaces 26 a, 28 a, 30 a,and 32 a of respective mold segments 26, 28, 30, 32. Likewise, all ofthe mold segments 22, 24, 26, 28, 30, 32 collectively define a mold ofthe present invention. The rear and front mold segments 26, 28, 30 and32 also include abutment surfaces 26 b, 28 b, 30 b, and 32 b; drivensurfaces 26 c, 28 c, 30 c, and 32 c; and sliding surfaces 26 d, 28 d, 30d, and 32 d. Likewise, left and right mold segments 22 and 24 includesliding surfaces 22 r, 22 f, and 24 r, 24 f for respective slidingengagement with sliding surfaces 26 d, 30 d, and 28 d, 32 d.

The rear mold segments 26 and 28, and the front mold segments 30 and 32,are slidably mounted to respective portions of the left and right moldsegments 22 and 24 using an interlocking guide rail arrangement.Interlocking guide rail arrangements are well known in the art ofmachine and tool design. In any case, guide rail support blocks 36 areT-jointed and fastened to respective portions of the left and right moldsegments 22 and 24. The guide rail support blocks 36 are provided forsupporting guide rails 38 thereon such as STAR brand guide rails. Theguide rails 38 are mounted to and fastened atop the support blocks 36and the respective sliding surfaces 22 r, 22 f, 24 r, 24 f of the leftand right mold segments 22 and 24. The guide rails 38 interengage withrunner blocks 40 such as STAR brand standard runner blocks, which aremounted to and fastened within channels (not shown), which are milledinto respective sliding surfaces of the mold segments. Accordingly, therear and front mold segments 26, 28, 30, 32 are slidable fore and aftalong the Y axis.

To slide the rear and front mold segments 26, 28, 30, 32 along the Yaxis, hydraulic cylinders 44 such as HEB brand cylinders are mounted tothe driven surfaces 26 c, 28 c, 30 c, and 32 c of the rear and frontmold segments 26, 28, 30, 32, preferably by a clevis arrangement (notshown). The hydraulic cylinders 44 are preferably of a self-locking typeand are supported by weldment brackets 46, which are mounted andfastened to the left and right mold segments 22 and 24 and to the leftand right base frames 14 and 16 as shown. Accordingly, the X axis motionof each of the left and right mold segments 22 and 24 is independentlycontrollable, and the Y axis motion of each of the rear and front moldsegments 26, 28, 30, 32 is independently controllable.

Shown in FIG. 3A, positioned just below the open mold cavity 34, is afour way spreader device defined partially by four vertically disposedspreader pins 48. Two-way spreader devices are well known in the art ofblow molding machine design. The four-way spreader, however, providesfour spreader pins, instead of two, that are movable radially outwardlywith respect to one another. Accordingly, the four-way spreader providesmore of a 360 degree contact with an article, compared with the 180degree contact of two-way spreaders of the prior art.

Positioned centrally of and just below the four-way spreader is a blowpin device 50. Blow pin devices are generally known in the art forcommunicating a gas under pressure with the interior of an article to beblow molded within the mold cavity of a blow mold. With the presentinvention, however, the blow pin device 50 includes a socket 52, or agripper device, for releasably holding a carrier 54 thereon.

The carrier 54 is an assembly that includes a main structural member anda plurality of components thereon, wherein the assembly is ultimatelyreceived within a final blow molded article. As defined herein, however,the carrier 54 may be any type of separate component or sub-assemblythat is suitable for insertion within a vessel or other blow moldedarticle. The carrier 54 may also function as a baffle or divider plate,which divides the volume of a finished, blow-molded, vessel into smallerportions and eliminates or reduces surging or splashing of large amountsof liquid within the finished vessel. Advantageously, the carrier 54 isat least locally connected, and preferably bonded or welded, to theinside of the finished vessel. To this end, the carrier 54 may have aplurality of feet or connecting elements (not shown) spaced along itsedges, which consist of a plastic material that is weldable or bondableto the inside of the finished vessel. The remainder of the carrier 54may therefore consist of a plastic material, which is not weldable orbondable to the material of the tank, or it may consist of a metal. Thecarrier 54 is similar to that disclosed in U.S. Patent ApplicationPublication 2001/0013516, which is assigned to the assignee hereof andis incorporated herein by reference.

Finally, a parison 56 is shown in cross-section and encircles the fourway spreader. The parison 56 is preferably a molten, plastic, tubularpreformed article. The parison 56 preferably comprises a plurality oflayers of different thermoplastic polymer materials that aresimultaneously extruded. For example, in a six layer co-extrusion of theparison 56 for making a vehicle fuel tank, the parison 56 has inner andouter structural layers of polyethylene (such as HDPE), and may have alayer of so-called “re-grind” or recycled scrap material between theouter layers, and a fuel vapor barrier layer (of ethylene vinyl alcoholor other polymer resistant to fuel vapor permeation) that is sandwichedbetween two adhesive layers which connect the vapor barrier layer to thestructural polymeric layers of re-grind and/or virgin HDPE.

FIG. 3B illustrates a cross-sectional view of the blow molding apparatus10 of FIG. 3A, taken along line 3B-3B. The open mold cavity 34 ispartially defined by the mold surfaces 22 a, 24 a, 26 a, 28 a of thevarious mold segments 22, 24, 26, 28. The blow pin device 50 and carrier54 are shown in a fully lowered or retracted position.

In a method according to one embodiment of the present invention, anextruder 58 produces the parison 56. The extruder 58 is preferably aco-extrusion device, which is well known in the art. The extruder 58essentially processes an input of plastic pellets to form an output of aco-extruded tubular preform of hot plastic, otherwise known as theparison 56. The parison 56 may be gravity fed directly to the open moldcavity 34 between or amongst the various mold segments 22, 24, 26, 28,30, 32. Alternatively, the parison 56 may be gripped by a transfermechanism (not shown), torn from the extruder 58, and transported intothe open mold cavity 34 for blow molding into a finished article orvessel, such as a fuel tank. In any case, the parison 56 is lowered to apoint where a lower end 60 of the parison 56 encircles the spreader pins48, which are in a closed or retracted position.

As shown in FIG. 3C, the spreader pins 48 are positioned within thelower end 60 of the parison 56. It is contemplated that the spreaderpins 48 can extend vertically upward deep into the interior of theparison if desired. In any case, the spreader pins 48 are movedlaterally apart, or radially outwardly. Accordingly, the spreader pins48 spread out the lower end 60 of the parison 56 to better distributethe parison material within the mold and to further open at least thelower portion of the parison 56.

Preferably after the four-way spreader has spread or opened the parison56, the blow pin device 50 and carrier 54 are extended upwardly into theparison 56 to an advanced position within the mold. The carrier 54 maybe loaded into the socket 52 of the blow pin device 50 manually orautomatically, such as by a robot (not shown). Blow pin devices 50 andthe means for advancing blow pin devices are generally well known in theart of blow molding. The present invention, however, contemplates theuse of rodless pneumatic cylinders, or pneumatic hollow rod cylinderssuch as HEB brand cylinders, in order to provide the blow pin advancingmotion. The hot parison 56 is somewhat molten, flexible and sticky, socare must be taken to maintain the parison 56 separate or spaced fromthe carrier 54. Ordinarily, a supply of pressurized air may be providedinto the parison 56 to maintain it open and prevent it from collapsingor otherwise engaging the carrier 54 prior to closing the mold. However,such a pre-blowing step is usually not necessary when using the fourequidistantly spaced spreader pins 48 of the four-way spreader device,which sufficiently keeps the parison 56 opened to prevent contact withthe carrier 54.

Preferably, when the blow pin device 50 and carrier 54 are extended tothe fully advanced position, the mold closes. Accordingly, FIG. 4illustrates the blow molding apparatus 10 in an advanced or completelyclosed position, wherein the left and right mold segments 22 and 24, andthe upper and lower mold segments 26, 28, 30, 32 have been advancedinwardly toward the now spread out parison 56. Preferably, the left andright mold segments 22 and 24 are advanced to a closed position first,and then the rear and front mold segments 26, 28, 30, 32 are advanced totheir closed positions although they could be closed in the reverseorder. Alternatively, all of the mold segments 22, 24, 26, 28, 30, 32may be advanced simultaneously so as to provide simultaneouscircumferential closure of the mold around the parison 56.

The mold is closed when the abutment surfaces 26 b and 28 b of the rearmold segments 26 and 28 abut one another and when abutment surfaces 30 band 32 b of the front mold segments 30 and 32 abut one another. Closureof the mold traps the parison 56 and closes its ends with the blow pindevice 50 extending into the parison 56 within the mold cavity 34.Preferably, the left and right mold segments 22 and 24 include a sealingaperture (not shown) for engaging and sealing around a portion of theblow pin device 50. As is well known in the art of blow molding, aportion of the extruded parison 56 is severed between the top of themold and the bottom of the extruder and another portion is severed belowthe bottom of the mold, such that the parison 56 remains intact withinthe mold and is sealed by the mold.

Desirably, as the mold is closed, the parison 56 engages feet (notshown) of the carrier 54 to limit or prevent relative movement betweenthe carrier 54 and the parison 56. To adhere to the parison 56, the feetare preferably a polymeric material directly bondable to the innermostlayer of the parison 18, such as HDPE or re-grind material. Theremainder of the carrier 54 can be made out of any material suitable foruse in the liquid fuel to be stored in the tank, including withoutlimitation, metals and polymers such as HDPE or re-grind material.

As shown in FIG. 5A, with the parison 56 positioned within the closedmold, pressurized air may be provided through apertures 62 of the blowpin device 50 to expand the parison 56 into engagement with the variousmold surfaces in order to form the final shape of the finished blowmolded article. The pressurized air may be at a pressure of about 10 barand, to facilitate cooling the parison 56 (which may be extruded atabout 250 degrees Celsius), the mold may be chilled to about 10 degreesCelsius using standard cooling passages formed within the various moldsegments.

FIG. 5B illustrates the parison fully blown and shaped into a finalmolded article 64 within the closed mold. After the blow molded article64 has cooled sufficiently to retain its shape, the supply ofpressurized air is turned off, the blow pin device 50 withdrawn, themold opened, and the blow molded article 64 removed.

FIG. 6 illustrates a partial cross-sectional view through the wall ofthe molded article 64. The molded article 64 is a multi-layer componentas described above and preferably includes six layers. For simplicity,the wall is shown as including a sensitive inner membrane 66 that issandwiched between an outer layer 68 and an inner layer 70. Forexemplary purposes, and referring to FIG. 6 and FIG. 3A, the partingline 72 results from the interface of the sliding surfaces 22 r and 26 dof the left mold segment 22 and rear left mold segment 26. Similarly,parting line 74 results from the interface of the abutment surfaces 26 band 28 b of the rear mold segments 26 and 28. Likewise, parting line 76results from the interface of the sliding surfaces 28 d and 24 r of therear right mold segment 28 and the right mold segment 24. Unlike priorart molding apparatuses and methods, however, the present invention doesnot result in large parting lines that yield ruptures in the innermembrane 66. Accordingly, the present invention enables fuel tanks to beblow molded without compromising the structural integrity of the layersthereof. In other words, the present invention yields fuel tanks inwhich the barrier layer 66 is imperforate so that no hydrocarbons canescape through any breaches or voids in the fuel tank wall.

FIGS. 7 through 11 illustrate another exemplary embodiment of thepresent invention. This embodiment is similar in many respects to theembodiment of FIGS. 3A-5B and like numerals between the embodimentsdesignate like or corresponding elements throughout the several views ofthe drawing figures. Accordingly, the common subject matter between theembodiments will generally not be repeated here.

FIG. 7 illustrates a blow molding apparatus 110 that is constructed foruse with a blow molding machine 112. The blow molding apparatus 110 isdepicted in plan view, looking downward along a Z axis or direction withan X axis extending left to right and a Y axis extending rear to front.As used herein, the term axis includes the term direction. As with thepreviously discussed embodiment, the blow molding apparatus 110 mayinclude left and right base frames (not shown) that are attached to leftand right movable platens or mold closers (not shown) of the blowmolding machine 112. Also like the previous embodiment, the blow moldingapparatus 110 includes a plurality of movable mold closures or segments122, 124, 126, 128, 130, 132, which are shown in FIG. 7 in a retractedor open position.

The plurality of movable mold segments includes a first pair of moldclosures that are substantially opposed to one another including a leftmold segment 122 mounted on the left base frame and a right mold segment124 mounted on the right base frame. Accordingly, the mold closers ofthe molding machine are capable of traversing the left and right moldsegments 122 and 124 between open and closed positions along the X axis.

A second pair of mold closures includes rear and front left moldsegments 126 and 130, which are slidably mounted to the left segment122, and a third pair of mold closures includes rear and front rightmold segments 128 and 132, which are slidably mounted to the rightsegment 124. In contrast to the previous embodiment, wherein likeopposed pairs of mold segments traverse along the Y axis, here the rearand front mold segments 126, 128 and 130, 132 are slidable between openand closed positions along the X axis. In other words, the rear andfront mold segments 126, 128 and 130, 132 move along substantially thesame axis as the left and right mold segments 122, 124. The rear andfront mold segments 126, 128 and 130, 132 need not be mounted to theirrespective left and right mold segments 122 and 124, but instead couldbe separately mounted to the blow molding machine 112. In any case thesecond pair of mold closures is substantially opposed to the third pair.

Each of the left and right mold segments 122 and 124 includes moldsurfaces 122 a and 124 a, which partially define a mold cavity 134. Themold cavity 134 is further defined by mold surfaces 126 a, 128 a, 130 a,and 132 a of respective mold segments 126, 128, 130, 132. Likewise, allof the mold segments 122, 124, 126, 128, 130, 132 collectively define amold of the present invention. The rear and front mold segments 126,128, 130 and 132 also include abutment surfaces 126 b, 128 b, 130 b, and132 b; driven surfaces (not shown) and sliding surfaces (not shown).Likewise, the left and right mold segments 122 and 124 include slidingsurfaces (not shown) for respective sliding engagement with the slidingsurfaces of the rear and front mold segments 126, 128, 130, and 132. Inother words, the rear and front mold segments 126, 128, 130, and 132 areadapted for slidable mounting with respect to the left and right moldsegments 122 and 124.

In general, slidable mounting arrangements are well known to those ofordinary skill in the art in machine tool design and any suitablearrangement may be used. The rear mold segments 126 and 128, and thefront mold segments 130 and 132, are independently, slidably mounted torespective portions of the left and right mold segments 122 and 124using an interlocking guide rail arrangement, as previously describedwith reference to the previous embodiment. Accordingly, the rear andfront mold segments 126, 128, 130, 132 are independently slidable sideto side along the X axis. To slide the rear and front mold segments 126,128, 130, 132 along the X axis hydraulic cylinders 144 are mounted tothe segments 126, 128, 130, 132, preferably by a clevis arrangement (notshown), as with the previously described embodiment. Accordingly, the Xaxis motion of each of the left and right mold segments 122 and 124 isindependently controllable, and the X axis motion of each of the rearand front mold segments 126, 128, 130, 132 is independentlycontrollable.

Also shown in FIG. 7, positioned just below the open mold cavity 134, isa four way spreader device defined partially by four vertically disposedspreader pins 148. Positioned centrally of and just below the four-wayspreader is a blow pin device 150 including a socket 152, or a gripperdevice, for releasably holding a carrier 154 thereon. Finally, a parison156 is shown in phantom lines and encircles the four way spreader.

Referring now to FIGS. 7 and 8 and to a method according to thisembodiment of the present invention, an extruder (not shown) producesthe parison 156, which may be gravity fed directly to the open moldcavity 134 between or amongst the various mold segments 122, 124, 126,128, 130, 132. Alternatively, the parison 156 may be gripped by atransfer mechanism (not shown), torn from the extruder, and transportedinto the open mold cavity 134 for blow molding into a finished articleor vessel, such as a fuel tank. In any case, the parison 156 is loweredto a point where a lower end 160 of the parison 156 encircles thespreader pins (not shown), which are in a closed or retracted position.The spreader pins are positioned within the lower end 160 of the parison156 and are moved laterally apart, or radially outwardly. Accordingly,the spreader pins spread out the lower end 160 of the parison 156 tobetter distribute the parison material within the mold and to furtheropen at least the lower end 160 of the parison 156. Preferably after thefour-way spreader has spread or opened the parison 156, the blow pindevice (not shown) and carrier (not shown) are extended upwardly intothe parison 156 to an advanced position within the mold. Preferably,when the blow pin device and carrier are extended to the fully advancedposition, the mold closes.

FIGS. 9 and 10 illustrate the blow molding apparatus 110 in an advancedposition, wherein the rear and front mold segments 126, 128, 130, 132have been advanced inwardly toward the parison 156. Preferably, the rearand front mold segments 126, 128, 130, 132 are advanced to their closedpositions first, and then the left and right mold segments 122 and 124are advanced to a closed position, although they could be closed in thereverse order. Alternatively, all of the mold segments 122, 124, 126,128, 130, 132 may be advanced simultaneously so as to providesimultaneous circumferential closure of the mold around the parison 156.Once the rear and front mold segments 126, 128, 130, 132 abut or areclosed respectively against one another as shown, the hydraulic pressurein the associated hydraulic cylinders 144 sharply rises or peaks.

When the hydraulic pressure peaks, the left and right mold segments 122,124 advance to close the mold, as better depicted in the cross-sectionalview of FIG. 11, wherein the left and right mold segments 122, 124 mayinclude abutment surfaces 122 r, 122 f, 124 r, 124 f that act asrespective opposed stops to stop travel of the mold segments 122, 124.The present invention contemplates, however, that the left and rightmold segments 122, 124 need not abut to define a closed mold condition.In other words, the mold may be considered “closed” at any predeterminedpoint after the abutment surfaces 126 b and 128 b of the rear moldsegments 126 and 128 abut one another and when abutment surfaces 130 band 132 b of the front mold segments 130 and 132 abut one another.

Closure of the mold traps the parison 156 and closes its ends with theblow pin device (not shown) extending into the parison 156 within themold cavity 134. A portion of the extruded parison 156 is severedbetween the top of the mold and the bottom of the extruder and anotherportion is severed below the bottom of the mold, such that the parison156 remains intact within the mold and is sealed by the mold. With theparison 156 positioned within the closed mold, pressurized gas, such asair, may be provided through the blow pin device to expand the parisoninto engagement with the various mold surfaces in order to form thefinal shape of the finished blow molded article. The parison is fullyblown and shaped into a final molded article within the closed mold.After the blow molded article has cooled sufficiently to retain itsshape, the supply of pressurized air is turned off, the blow pin devicewithdrawn, the mold opened, and the blow molded article removed.

As depicted by FIG. 12, with this invention it is now possible tointegrally blow mold a bulbous or hollow flange portion 180 and anarrower portion 182 of a relatively narrow and generally tubular orcylindrical hollow vessel such as a “cigar-shaped” fuel tank 164. Theflange portion 180 is adapted to be a fuel inlet portion of the tank164, wherein a fuel inlet 184 is mounted thereto. The narrower portion182 is adapted to be packaged in a tunnel along a centerline, andbetween seats, of a vehicle to which the tank 164 is assembled. Thedifference in size or “diameter” between the flange portion 180 and thenarrower portion 182 is at least about 2:1. The sliding mold segments ofthe present invention are capable of opening or retracting alongmultiple axes, which facilitates use of a relatively larger parison thanbefore possible. In turn, using a larger parison translates into areduced stretch ratio when blow molding the parison. This is because thelarger parison can be sized to approximate the size of the interior of anarrower portion of the mold cavity compared to a relatively largerflange portion of the mold cavity. The narrower portion of the moldcavity is used to mold the narrower portion of the tank 164 and thelarger flange portion of the mold cavity is used to mold the flangeportion 180 of the tank 164.

Accordingly, the difference in diameter between the larger flangeportion of the mold cavity and the narrower portion of the mold cavitymay be about 2:1. In accordance with the present invention, a portion ofthe larger parison is expanded very little or just enough to engage thenarrower portion of the mold cavity, and another portion of the largerparison is expanded in accordance with a standard, acceptable stretchratio to engage the larger flange portion of the mold cavity. In otherwords, and as an example, the larger parison may undergo a stretch ratioof about 1:1 in the narrower portion of the mold cavity and a stretchratio of about 2:1 in the larger flange portion of the mold cavity. Thisrelatively low stretch ratio ensures that the material being blow moldedhas a relatively uniform wall thickness and does not rupture or becometoo thin.

In contrast, with conventional two-piece molds and using conventionalblow molding methods, such a configuration would require much largerdifferences in stretch ratios between a relatively narrow portion of amold cavity and a relatively larger flange portion of a mold cavity. Forexample, a conventional approach would require using a relativelysmaller parison that would undergo a stretch ratio of about 1:1 to 2:1in the narrower portion of the mold and a stretch ratio of about 3:1 to2:1 in the larger flange portion of the mold. Thus, the presentinvention provides a significant improvement in the art of blow moldingthat yields lower stretch ratios and more uniform wall thickness of blowmolded components, and that avoids excessive flash and rupturing ofsensitive inner membranes.

Using movable mold segments that traverse in a plurality of generallytransverse axes, permits using a larger parison, which in turn,accommodates use of a “Ship-in-a-Bottle” fuel tank and carrier design. Alarger parison has a larger internal diameter, which facilitatesinserting larger carriers therein during a blow molding process. In thepast, it has sometimes been required to manufacture a fuel tank from twohalf-shells in order to accommodate assembly of a carrier or largecomponents within the fuel tank. Such fuel tank manufacturing techniquestend to be more difficult and costly than fuel tank blow moldingtechniques and tend to have unacceptably high hydrocarbon permeationlosses. Thus, the present invention provides a method of blow moldingfuel tanks that is less expensive than prior art methods and thatresults in a fuel tank with comparably higher structural integrity andsignificantly lower hydrocarbon permeation losses.

While the forms of the invention herein disclosed constitute a presentlypreferred embodiment, many others are possible. For instance, the moldsegments may be independently arranged and not mounted to one another,and the mold segments may move in oblique axes other than theperpendicularly oriented X and Y axes. It is not intended herein tomention all the possible equivalent forms or ramification of theinvention. It is understood that terms used herein are merelydescriptive, rather than limiting, and that various changes may be madewithout departing from the spirit and scope of the invention as definedby the following claims.

1. A method of blow molding an article from a parison in a cavity of ablow mold comprising the steps of: providing a first pair of moldclosures, each having a mold cavity surface and movable in the directionof a first axis between open and closed positions; providing a secondpair of mold closures, each separate from the first pair of moldclosures, each having an abutment surface and a separate mold cavitysurface, and each being carried by the same one closure of the firstpair of mold closures; providing a third pair of mold closures, eachseparate from both the first pair and the second pair of mold closures,each having an abutment surface constructed for engagement with theabutment surface of a respective one of the mold closures of the secondpair of mold closures, each having a separate mold cavity surface, andeach being carried by the same other closure of the first pair of moldclosures; positioning a molten plastic parison with a plurality oflayers including a fuel vapor barrier layer between the first, second,and third pairs of mold closures before the mold is closed; advancingthe first pair of mold closures in the direction of the first axis toclose the first pair of mold closures without pinching the parison andprior to blow molding the parison; advancing the second pair of moldclosures and the third pair of mold closures into engagement of theabutment surfaces of the second pair of mold closures with the abutmentsurfaces of the third pair of mold closures without pinching theparison; and advancing relative to the first pair of mold closures thesecond pair of mold closures in the direction of a second axis and thethird pair of mold closures in the direction of a third axis parallel tothe second axis in order to close the blow mold and position their moldcavity surfaces to form a closed mold cavity, wherein the mold is closedwithout the abutment surfaces engaging the parison and without pinchingthe parison between any of the entirety of the abutment surfaces as aresult of closing the blow mold and before blow molding the parison inthe closed mold cavity so that the parison is blow molded in the closedmold cavity without forming any heavy flash and without rupturing thefuel vapor barrier layer, wherein the first, second, and third axes areseparate from one another, and wherein the first axis is perpendicularto the second and third axes.
 2. The method of claim 1 furthercomprising the step of providing a carrier assembly within an interiorof said parison.
 3. The method of claim 2 further comprising the stepsof: mounting said carrier assembly to a blow pin; and extending saidblow pin with said carrier assembly mounted thereto into the interior ofsaid parison.
 4. The method of claim 3 further comprising the step ofinjecting a pressurized gas within the interior of said parison toexpand said parison outwardly within said mold closures.
 5. The methodof claim 1 wherein both the second and third pairs of mold closures areclosed before blowing the parison into engagement with the second andthird pairs of mold closures to produce a blow molded article withoutpinching the parison along any of at least three parting lines resultingfrom interfaces of said mold closures extending along the article oneach of opposite sides of the article.
 6. The method of claim 1 furthercomprising the step of providing a carrier assembly within an interiorof the parison before blow molding the parison into engagement with theclosed mold closures.
 7. The method of claim 1 further comprising thesteps of: mounting a carrier assembly to a blow pin; and extending theblow pin with the carrier assembly mounted thereto into the interior ofthe parison before blow molding the parison into engagement with theclosed mold closures.
 8. The method of claim 6 further comprising thesteps of: injecting a pressurized gas within the interior of theparison; retracting the first pair of mold closures along the firstaxis; and removing a molded article formed from the parison.
 9. Themethod of claim 8 further comprising the steps of advancing the firstpair of mold closures in the direction of said first axis transverse tosaid second and third axes into abutment with each other and to engagethe abutment surfaces of the second pair of mold closures with theabutment surfaces of the third pair of mold closures before blowing theparison into engagement with the mold closures to produce a blow moldedarticle without pinching the parison along any of at least three partinglines resulting from interfaces of said mold closures and extendingalong the article on each of opposite sides of the article.
 10. A methodof blow molding comprising the steps of: providing left and right sidemold segments movable in the direction of a first axis; providing leftand right rear mold segments, each having a mold surface and a separateabutment surface, and each respectively slidably carried by the left andright side mold segments; providing left and right front mold segments,each having a mold surface and a separate abutment surface, and eachrespectively slidably carried by the left and right side mold segments;positioning a molten plastic parison with a plurality of layersincluding a fuel vapor barrier layer between the left and right side,rear, and front mold segments before the mold is closed; advancing theleft side mold segment and the right side mold segment toward each otherin the direction of the first axis to engage the side mold segmentswithout pinching the parison between the side mold segments; advancingthe abutment surfaces of the front and rear left mold segments intoengagement with the respective abutment surfaces of the front and rearright mold segments without pinching the parison by the abutmentsurfaces of these front and rear mold segments; advancing the rear leftmold segment toward the front left mold segment in the direction of asecond axis substantially perpendicular to the first axis; advancing therear right mold segment toward the front right mold segment in thedirection of a third axis separate from and substantially parallel tothe second axis and substantially perpendicular to the first axis inorder to form a closed mold, wherein the parison is not pinched betweenany of the entirety of the mold segments as a result of closing themold; injecting a pressurized gas into the interior of the parison afterclosing the mold so that the parison is blow molded in the closed moldcavity without forming any heavy flash, without pinching the parisonbetween any of the entirety of the mold segments, and without rupturingthe fuel vapor barrier layer; retracting the side mold segments in thedirection of the first axis; and removing the molded article formed fromthe parison.
 11. The method of claim 10 further comprising the step ofproviding a carrier assembly within an interior of said parison.
 12. Themethod of claim 11 further comprising the steps of: mounting saidcarrier assembly to a blow pin; and extending said blow pin with saidcarrier assembly mounted thereto into the interior of said parison. 13.The method of claim 10 further comprising the steps of advancing saidside mold segments along said first axis into abutment with each otherand to engage the abutment surfaces of the left rear and front moldsegments with the right rear and front mold segments respectively beforeblowing the parison into engagement with the mold segments to produce ablow molded article without pinching the parison along any of at leastthree parting lines extending along the molded article on each ofopposite sides of the molded article and resulting from interfaces ofsaid mold segments.
 14. The method of claim 10 further comprising thestep of: providing a pressurized gas into said parison to expand saidparison into engagement with said mold segments in order to form a blowmolded article, wherein said parison undergoes a stretch ratio of aboutone-to-one to form a narrower portion of said blow molded article andanother stretch ratio of about two-to-one to form a larger flangeportion of said blow molded article.
 15. A method of blow molding anarticle from a parison having a vapor barrier layer within a cavity of ablow mold, said method comprising the steps of: providing a first pairof opposed mold closures each having a mold surface, a second pair ofmold closures each having a mold surface and a separate abutment surfaceand each carried by the same one mold closure of said first pair of moldclosures, and a third pair of mold closures each having a mold surfaceand a separate abutment surface and each carried by the same other moldclosure of said first pair of mold closures, wherein said third pair ofmold closures is substantially opposed to said second pair of moldclosures; positioning said parison between said first pair of moldclosures before the mold is closed; advancing said first pair of moldclosures substantially toward one another along a first axis in a firstaxial direction; and advancing at least one of said second or thirdpairs of mold closures relative to the other of said second or thirdpairs of mold closures independently of advancing the first pair of moldclosures toward one another, wherein the abutment surfaces of the secondpair of mold closures are engaged with the abutment surfaces of thethird pair of mold closures as a result of closing the mold and withoutany of the abutment surfaces engaging the parison, wherein the parisonis not pinched between any of the entirety of the abutment surfaces as aresult of closing the mold and before blow molding the parison in theclosed mold cavity, wherein the parison is blow molded in the closedmold cavity without forming any heavy flash and in order to form anarticle therefrom, wherein said advancing step further includesadvancing one of said second pair of mold closures substantially towardone of said third pair of mold closures along a second axis that issubstantially parallel to said first axis and advancing the other ofsaid second pair of mold closures substantially toward the other of saidthird pair of mold closures along a third axis that is substantiallyparallel to said first and second axes, and wherein the first, second,and third axes are separate from one another.
 16. The method of claim 15wherein said advancing step includes advancing the abutment surfaces ofsaid second pair of mold closures substantially into engagement with theabutment surfaces of said third pair of mold closures substantially inthe first axial direction.
 17. The method of claim 15 further comprisingthe steps of: injecting a pressurized gas into the interior of saidparison; retracting said first, second, and third pairs of moldclosures; and removing said article formed from said parison.
 18. Themethod of claim 17 further comprising the step of providing a carrierassembly within the interior of said parison.
 19. The method of claim 18further comprising the steps of: mounting said carrier assembly to ablow pin; and extending said blow pin with said carrier assembly mountedthereto into the interior of said parison.
 20. The method of claim 15further comprising the step of: providing a pressurized gas into saidparison to expand said parison into engagement with said mold closuresin order to form a blow molded article, wherein said parison undergoes astretch ratio of about one-to-one to form a narrower portion of saidblow molded article and another stretch ratio of about two-to-one toform a larger flange portion of said blow molded article.
 21. The methodof claim 15 further comprising the steps of advancing said first pair ofmold closures in said first axial direction into abutment with eachother and to engage the abutment surfaces of the second pair of moldclosures with the abutment surfaces of the third pair of mold closuresbefore blowing the parison into engagement with the mold closures toproduce a blow molded article without pinching the parison along any ofat least three parting lines extending along the article on each ofopposite sides of the article and resulting from interfaces of said moldclosures.
 22. The method of claim 15 further comprising the steps ofadvancing said first pair of mold closures in said first axial directioninto abutment with each other and to engage the abutment surfaces of thesecond pair of mold closures with the abutment surfaces of the thirdpair of mold closures before blowing the parison into engagement withthe mold closures to produce a blow molded fuel tank without pinchingthe parison along any of at least three parting lines extending alongthe fuel tank on each of opposite sides of the fuel tank and resultingfrom interfaces of said mold closures.
 23. The method of claim 15wherein the second and third pairs of mold closures are advanced intoengagement of their respective abutment surfaces with one another andsubsequently the first pair of mold closures is advanced toward oneanother.
 24. The method of claim 15 further comprising the steps ofadvancing the second and third pairs of mold closures into engagement oftheir respective abutment surfaces with each other before blowing theparison into engagement with the mold closures to produce a blow moldedarticle without pinching the parison along any of at least three partinglines extending along the article on each of opposite sides of thearticle and resulting from interfaces of said mold closures.